Flameless atomic absorption spectrophotometry (FAAS) and neutron activation analysis (NAA) have been used for quantitation of vanadium, platinum, calcium, iron, cobalt and some other elements in biological tissues and fluids. The analyses are important in clinical biochemical, pharmacokinetic, and binding studies. Very sensitive analytical techniques are necessary because, in some instances, the elements are present in trace concentrations (i.e. typically in the part-per-million (10 to the minus 6 g/g) or part-per-billion (PPB)(10 to the minus 9 g/g) level and less frequently at the part-per-trillion (PPT) 10 to the minus 12 g/g level, and, in many cases, the sample size is small as well (i.e. less than l ml). Elemental Electron Probe Microanalysis has been performed using a Cameca MBX instrument equipped with a transmission microscope (Creteil, France) to localize several elements, platinum, iron and sulfur on the microscopic scale in different tissues. Separation techniques including ion-exchange chromatography, solvent extraction, and electrophoresis have been used to purify samples, fractionate and concentrate chemical species before analysis, and eliminate substances interfering with trace level assays.